The invention is directed to diesters of naphthalene dicarboxylic acid. More particularly, the invention is directed to the use of diesters of naphthalene dicarboxylic acid that are surprisingly effective in photochemically stabilizing dibenzoylmethane derivatives, absorbing UV radiation, and which can be used to increase the emolliency and sunscreen protection factor (SPF) of cosmetic formulations. The diesters of naphthalene dicarboxylic acid are also useful for imparting gloss and for stabilizing natural hair color and hair dyes against fading, and to impart gloss to hair.
It is well known that ultraviolet light having a wavelength between about 280 nm or 290 nm and 320 nm (UV-B) is harmful to human skin, causing burns that are detrimental to the development of a good sun tan. UV-A radiation, while producing tanning of the skin, also can cause damage, particularly to very lightly colored, sensitive skin, leading to reduction of skin elasticity and wrinkles.
Therefore, a sunscreen composition should include both UV-A and UV-B filters to prevent most of the sunlight within the full range of about 280 nm to about 400 nm from damaging human skin.
The UV-B filters that are most widely used commercially in sunscreen compositions are paramethoxycinnamic acid esters, such as 2-ethylhexyl paramethoxycinnamate, commonly referred to as octyl methoxycinnamate or PARSOL(copyright) MCX, having an ethyl radical extending from the 2 position of the hexyl long chain backbone; oxybenzone; and octyl salicylate.
The UV-A filters most commonly used in commercial sunscreen compositions are the dibenzoylmethane derivatives, particularly 4-(1,1-dimethylethyl)-4xe2x80x2-methoxydibenzoylmethane (PARSOL(copyright) 1789), and 4-isopropyl dibenzoylmethane (EUSOLEX 8020). Other dibenzoylmethane derivatives described as UV-A filters are disclosed in U.S. Pat. Nos. 4,489,057; 4,387,089 and 4,562,067 and 5,670,140, hereby incorporated by reference. It is also well known that the above described and most commonly used UV-A filters, particularly the dibenzoylmethane derivatives, such as PARSOL(copyright) 1789, suffer in photochemical stability (also called photostability) when used alone or in combination with the above-described most commercially used UV-B filters. Accordingly, when used alone or when combined with a UV-B filter, such as 2-ethylhexyl paramethoxycinnamate (PARSOL(copyright) MCX), oxybenzone and/or octyl salicylate, the PARSOL(copyright) 1789 becomes less photochemically stable, necessitating repeated, frequent coatings over the skin for sufficient UV radiation protection.
In accordance with one embodiment of the invention, it has been found, quite surprisingly, that by including one or more diesters of naphthalene dicarboxylic acid of formula (I) into a cosmetic sunscreen formulation containing a UV-A dibenzyolmethane derivative, particularly PARSOL(copyright) 1789, and/or 4-isopropyl dibenzoylmethane (EUSOLEX 8020), the dibenzyolmethane derivative is photochemically stabilized so that the dibenzyolmethane derivative-containing sunscreen composition, with or without additional sunscreen agents, such as oxybenzone and/or octyl methoxycinnamate (ESCALOL 567), is more effective for filtering out UV-A radiation; the composition filters more UV-A radiation for longer periods of time; and, therefore, the sunscreen formulation need not be applied to the skin as frequently while maintaining effective skin protection against UV-A radiation.
In accordance with another important advantage of the invention, the diesters of naphthalene dicarboxylic acids can also absorb UV light in the most damaging range of about 280 nm to 300 nm, especially over the 280 nm to 295 nm wavelength absorbance range.
By the addition of UV-B filter compounds, such as octyl methoxycinnamate, octyl salicylate, and/or oxybenzone, the compositions of the invention can maintain surprisingly effective hair color protection and can protect against UV radiation both in the UV-A and UV-B range, with or without common sunscreen additives, such as octocrylene, and/or titanium dioxide. The composition reaches a surprisingly high SPF without solid additives, such as titanium dioxide, thereby providing an exceptionally elegant feel that can be applied easily in a continuous coating for complete coverage and sunscreen protection. In the preferred compositions, the ratio of UV-A to UV-B filter compounds is in the range of about 0.1:1 to about 10:1, preferably about 0.1:1 to about 3:1, more preferably about 0.1:1 to about 0.5:1, most preferably about 0.3:1 to about 0.5:1. The preferred compositions of the invention achieve unexpectedly high SPF, e.g., higher than SPF 12, or higher than SPF 20, with the addition of surprisingly low amounts of other UV-B and UV-A filters to the PARSOL 1789, and without solid blocking compounds, such as TiO2.
In accordance with another embodiment of the invention, the diesters of naphthalene dicarboxylic acid of the invention impart gloss to hair, and/or stabilize hair color against fading, particularly for hair containing a synthetic dye.
In addition, clear or transparent cosmetic formulations are particularly desirable because the consumer likens transparency to purity, and because transparent formulations have esthetic and functional appeal. Clear cosmetic formulations sometimes have been difficult to maintain stable and clear, but have been developed in each of the following areas: clear roll-ons and gels for antiperspirants; clear gel curl activators (hair moisturizers with relatively high levels of polyols); clear cosmetic sticks, including deodorant sticks and antiperspirant sticks; clear solutions; clear suntan oils; clear transdermal drug administration solutions, e.g., clear benzocaine solutions; clear aftershave compositions; transparent gel toothpastes; and clear lipsticks.
In accordance with another aspect of the invention, one or more diesters of naphthalene dicarboxylic acid of formula (I) can be included in cosmetic formulations, whether in the form of emulsions or anydrous compositions, while providing sunscreen protection to the area of the body coated with the cosmetic formulation and, in addition, can be included in a cosmetic formulation to increase the refractive index of the oil phase to more closely equal the refractive index of the water phase such that when the two phases are mixed and emulsified, the formulation will be clear or transparent.
In brief, the invention is directed to dibenzoylmethane derivative-stabilizing and/or skin protecting and/or gloss-imparting and/or hair color protecting compounds comprising a diester of a naphthalene dicarboxylic acid, while providing UV absorption.
The active dibenzoylmethane derivative-stabilizing and/or skin protecting and/or gloss-imparting and/or hair color protecting compounds of the invention are diesters of a naphthalene dicarboxylic acid.
A diester of the invention has the structure (I): 
wherein R1 has the formula (II), 
wherein k is 1 to 13, preferably 1 to 6, most preferably 1, and R2, same or different, is selected from the group consisting of a compound of formula (II) wherein k is 1 to 13, preferably 1 to 6, most preferably 1, and an alkyl group, straight chain or branched, having 1 to 22 carbon atoms, and mixtures thereof.
The diesters are reaction products of (a) a naphthalene dicarboxylic acid having the structure (III): 
and an alcohol having the structure R2xe2x80x94OH, wherein R2 is defined as above, or a mixture thereof.
The naphthalene dicarboxylic acid is selected from the group consisting of 1,2-naphthalene dicarboxylic acid; 1,3-naphthalene dicarboxylic acid; 1,4-naphthalene dicarboxylic acid; 1,5-naphthalene dicarboxylic acid; 1,6-naphthalene dicarboxylic acid; 1,7-naphthalene dicarboxylic acid; 1,8-naphthalene dicarboxylic acid; 2,3-naphthalene dicarboxylic acid; 2,6-naphthalene dicarboxylic acid; 2,7-naphthalene dicarboxylic acid, and mixtures thereof. Preferred dicarboxylic acids are the 2,6-, 1,5- and 1,8-naphthalene dicarboxylic acids.
The alcohol R2xe2x80x94OH can be, for example, methanol, ethanol, propanol, isopropyl alcohol, n-butanol, sec-butanol, isobutyl alcohol, tert-butyl alcohol, amyl alcohol, 1-hexanol, 1-octanol, 1-decanol, isodecyl alcohol, 1-undecanol, 1-dodecanol, 1-tridecyl alcohol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol, 1-eicosonol, 1-decosonol, 2-ethylhexyl alcohol, 2-butyloctanol, 2-butyldecanol, 2-hexyldecanol, 2-octyldecanol, 2-hexyldodecanol, 2-octyldodecanol, 2-decyltetradecanol, cinnamyl alcohol (cinnamic alcohol), and mixtures thereof.
Surprisingly, it has been found that compounds having formula (I) are quire effective in photochemically stabilizing dibenzoylmethane derivatives.
Accordingly, one aspect of the invention is to provide a composition for application to human skin and hair that photochemically stabilizes dibenzoylmethane derivatives, particularly PARSOL(copyright) 1789, and capable of increasing the sunscreen protection factor (SPF) achievable for sunscreen compositions containing the dibenzoylmethane derivatives.
Another aspect of the invention is to provide an improved, stable composition containing a diester of a naphthalene dicarboxylic acid that increases the effectiveness of dibenzoylmethane derivative sunscreen compounds, particularly 4-(1,1-dimethylethyl)-4xe2x80x2-methoxydibenzoylmethane (PARSOL(copyright) 1789), in SPF and in duration, for protection of human skin and hair.
Another aspect of the invention is to provide a stable, broad spectrum sunscreen composition for topical application to human skin and hair that has a SPF of at least 12 and provides substantial protection against the full range of solar UV radiation (280-400 nm), including about 4-15% by weight of a diester of naphthalene dicarboxylic acid, and contains less than 7% and preferably less than 6.1% of sunscreen composition additives selected from the group oxybenzone and avobenzone (PARSOL 1789).
Still another aspect of the invention is to provide a moisturizing composition for topical application to human skin and hair that provides an SPF of at least 20, including about 4-15% by weight of a diester of naphthalene dicarboxylic acid.
These diesters of naphthalene dicarboxylic acids are quite effective in imparting hair gloss and preserving a desired natural or dyed hair color, while providing the hair with sunscreen protection, when contained in a composition in an amount of at least about 0.1% by weight, up to about 20% by weight, preferably about 0.2% to 10% by weight, more preferably about 0.5% to 10% by weight.
Accordingly, another aspect of the invention is to provide a composition that includes a diester of one or more naphthalene dicarboxylic acids as a hair gloss-imparting compound, and as a hair color preserving compound, said naphthalene dicarboxylic acid diester compounds having formula (I).
These diesters of naphthalene dicarboxylic acids are also quite effective in formulating clear or transparent cosmetic formulations, having increased emolliency, and in providing UV sunlight protection to skin.
Thus, another aspect of the invention is directed to cosmetic formulations that include one or more emollients and/or skin conditioners, such as a silicone fluid, wherein the cosmetic compositions are useful as antiperspirants, deodorants, emollients, moisturizers, suntan oils, after-shave compositions, transdermal drug compositions, and the like. In the preferred embodiment, the cosmetic formulations comprise an emulsion of an oil phase and a water phase, wherein the water phase includes an emollient, humectant or other organic compound that increases the refractive index of the water phase, and the oil phase includes a sufficient amount of particular diesters of naphthalene dicarboxylic acids to provide the oil phase and the water phase of the cosmetic formulations with approximately the same refractive index, so that the cosmetic formulations are transparent, or clear, as perceived by human eye. In other embodiments, the clear cosmetic formulations may be anhydrous, or include only an oil phase, with thickening agents such as one or more clays, e.g., hectorite or laponite, so that no emulsifying agents are required, but the composition includes one or more of the particular diesters of a naphthalene dicarboxylic acid for emolliency and clarity.
Preferred diesters of naphthalene dicarboxylic acid of the invention have a high refractive index of at least about 1.5, preferably about 1.53, and are added to the oil phase of a oil and water emulsion to provide emolliency and, optionally, transparency to the emulsion, particularly for cosmetic formulations.
The above and other aspects and advantages of the invention will become more apparent from the following detailed description of the preferred embodiments, taken in conjunction with the drawings.